The present work demonstrates the production of chlorapatite (ClAp) through thermal decomposition of chemically treated fish scales, originating from an Amazon fish species (Arapaima gigas). The scales were treated with hydrochloric acid (HCl) solution for deproteinization. Afterwards, the solution was neutralized by sodium hydroxide (NaOH) treatment to obtain an apatite-rich slurry. The heat treatment was carried out at different temperatures including 600 °C, 800 °C, and 1000 °C. The powders obtained were characterized through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM). The XRD analysis and FTIR spectra confirmed the incorporation of chlorine into the apatite structure. The FTIR results showed absorption bands relative to the OH^–, PO₄³⁻ functional groups which are a characteristic of chlorapatite. Moreover, the intensity of the OH–Cl elongation could be observed. Chlorapatite Ca₅(PO₄)₃Cl, NaCl, and NaCaPO₄ phases were identified, achieving up to 87.4 wt% for ClAp. The SEM observations show that with increasing temperature, the ClAp obtained consists of slightly larger, more crystalline grains. Furthermore, the grains ranged in size, between 1-5 μm and ClAp1000 sample recorded crystallinity of 84.27%. ClAp and NaCaPO₄ can be used in electronics as phosphor materials due to their luminescence and biomedical applications.

The subject of rock–fluid interaction is important in cases where flow through porous media is occurring. One special case is when the fluid reacts with the porous matrix. In this case, the mass transfer and reaction rate control the dissolution pattern. This article aimed to study the interaction between an acid nanoemulsion system and a carbonate porous media. Nanoemulsions were developed to retard the rock’s dissolution and to promote the formation of conductivity channels. Nanoemulsions were prepared using ALK100 (alkyl alcohol ethoxylate) and RNX110 (alkylphenol ethoxylate) (nonionic surfactants), sec-butanol (co-surfactant), xylene isomers (oil phase), and a solution of HCl (aqueous phase). The obtained systems were characterized in terms of surface tension, droplet diameter, and reactivity. X-ray fluorescence/diffraction (XRF/XRD) and X-ray microtomography (microCT) were performed on carbonate porous media samples treated with the acid systems in order to observe the effects of the fluid–rock interaction. The results showed that the acid nanoemulsion, presenting a low oil content formulation, showed the low surface tension and droplet size characteristic of nanoemulsions. It was experimentally verified that the reactivity in the nanoemulsion media was mass-transfer-retarded, and that the wormhole pattern was verified under the studied conditions.

Aromatic solvents, such xylene and toluene, are widely used in the organic damage removal operations, although increasing environmental requirements have encouraged the research for new environmental-friendly solutions to replace these solvents. Microemulsions are thermodynamically stable multicomponent systems known by their notable solubilization capability. This paper describes the preparation and investigation of a low-oil-content microemulsion system able to remove the organic damage and restore the permeability. The damage removal efficiency, for the microemulsion systems prepared, was comparable to xylene. The results showed that the proposed microemulsion formulation is a cost-effective and environment-friendly alternative to aromatic solvents.

A adsorção tem se destacado como um processo eficaz na remoção corantes sintéticos nos efluentes industriais, e a utilização de precursores sustentáveis, tem sido investigada na obtenção de carvão ativado. O objetivo deste trabalho foi avaliar o potencial do carvão ativado produzido da casca da sacha-inchi (CSI) como adsorvente na remoção do corante aniônico alaranjado de metila (ALM). O CSI foi sintetizado por ativação química com H3PO4 e carbonização da biomassa da sacha-inchi a 500 C por 1h. Os materiais foram caracterizados quanto às propriedades químicas e texturais. Ensaios cinéticos foram realizados em batelada e os dados experimentais ajustados aos modelos de pseudo-primeira ordem e pseudo-segunda ordem. As características do equilíbrio de adsorção foram determinadas pelas isotermas de Langmuir, Freundlich e Temkin. Os resultados mostraram a produção de um carvão ativado de alta qualidade com área superfícial específica elevada (1255 m2 g-1), com remoção do ALM de 96,5% e uma cinética de adsorção melhor descrita pelo modelo de pseudo-segunda ordem. A isoterma de Langmuir apresentou o melhor ajuste, revelando uma adsorção em monocamada, com capacidade máxima de 250 mg g-1. A valorização dos resíduos da sacha-inchi em carvão ativado favorece para uma maior sustentabilidade ambiental e permitiu obter um adsorvente eficaz para a remoção do ALM.